FAQ & Troubleshooting¶

Could NOT find CFITSIO

Solution: Install the development headers:

sudo apt-get install libcfitsio-dev

sudo yum install cfitsio-devel

Or build without cfitsio:

cmake .. -DUSE_CFITSIO=OFF

See Build Tiers and Compile Instructions for details.

fatal error: readline/readline.h: No such file or directory

Solution: Install the development headers, or build without CLI:

sudo apt-get install libreadline-dev libncurses5-dev

cmake .. -DUSE_CLI=OFF

error while loading shared libraries: libImageStreamIO.so

Solution: Add the install directory to the linker path:

echo "/usr/local/lib" > usrlocal.conf
sudo mv usrlocal.conf /etc/ld.so.conf.d/
sudo ldconfig

export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH

Cannot open /milk/shm/stream.im.shm: Permission denied

Solution: Ensure the SHM directory exists and is writable:

sudo mkdir -p /milk/shm
sudo chmod 1777 /milk/shm

For best performance, mount as tmpfs:

echo "tmpfs /milk/shm tmpfs rw,nosuid,nodev" | sudo tee -a /etc/fstab
sudo mount /milk/shm

Old .im.shm files from crashed processes can interfere.

Solution:

milk-shmimpurge              # (1)!
milk-shmim-rm <streamname>   # (2)!

1. Remove all stale SHM files.
2. Remove a specific stream.

The default shared memory directory is /milk/shm. Override with:

export MILK_SHM_DIR=/path/to/custom/shm

ERROR: FPS already exists

Solution: Remove the stale FPS, then retry:

milk-fps-set <fpsname> ..delete

Ensure the processinfo SHM directory exists and processes are registered:

ls $MILK_SHM_DIR/proc.*.shm   # (1)!
milk-procinfo-list             # (2)!

1. Check for processinfo files
2. Scan for processes

If standalone executables launched with -tmux don't appear:

1. Ensure tmux is installed: which tmux
2. Check if the tmux session exists: tmux ls
3. Verify the FPS name has no spaces or special characters.

This can happen when the startup banner clears the screen.

Solution: This is a known cosmetic issue. The prompt will stabilize after the first command.

Unknown command: mycommand

Solution: Check that the module is loaded:

milk-cli > m?                      # (1)!
milk-cli > h? mycommand            # (2)!

1. List all loaded modules
2. Search for a command

If the module is a plugin, ensure it was compiled and the .so file is in the library path.

For latency-critical applications (AO loops), configure real-time scheduling:

milk-makecsetandrt           # (1)!
milk-cli -p 90               # (2)!

1. Create cpuset, enable RT
2. Launch with high priority

Benchmark semaphore performance:

milk-semloopspeed

Typical values: >100 kHz on modern hardware.